Something about eyeball gore just feels particularly disturbing. Since the eye is such a sensitive and vulnerable part of the body, people typically rush to defend that area first when faced with incoming injury, closing their eyes and raising their hands above their face. Perhaps it is the idea of having to witness one's own torture that makes the concept of eye gouges so horrifying, or maybe it stems from the same reasons people fear contact lenses. Plus, eyes are basically squishy jelly, and are kind of gross if you think about them for too long.
Often accompanied by first-person shots, these eyeball gore scenes tap into the audience's own voyeurism to scare you. Scenes of ocular gore torture you in the way a car crash begs your attention, and these nasty horror movies fully utilize the eye gouge for the most gore-oriented viewers. Beware, as these scenes can't be unseen, unless of course you're the one experiencing them.